Abstract: In photographic equipment for reading magnetically recorded data on a film strip, gradual degradation of the read data signal caused, for example, by material buildup on the magnetic read head is detected by monitoring the read data signal to indicate when the signal falls below a normal signal level but is still above a minimum threshold at which data loss would result. Apparatus useful for this purpose includes first and second comparators for sensing the decline of the data signal level into a range falling between a first predetermined normal signal level threshold and a second lower predetermined signal level preferably at or slightly above minimum detectable signal level. With such an arrangement, even though data is still capable of being read and decoded, the operator of the data read equipment is given advance warning of the incipient read data problem sufficiently in advance of read failure condition to allow corrective action, e.g. cleaning of the read head, before actual data read failures occur.